1. Field of the Invention
The present invention relates to a color television transmission system wherein a color-sync signal and digital sound signals from at least one sound channel are transmitted in the horizontal blanking intervals during the period of the back porch, with the color-sync signal and the digital sound signals separated from each other.
2. Description of the Prior Art
A color television transmission system of the type to which this invention relates is shown in German Published Patent Application (DT-OS) No. 2,350,477.
It comprises transmitting and receiving equipment and, if necessary, relay stations of television links where for reasons of frequency economy, no sound channels are provided for the sound signals. The sound signals are "integrated in the video signal," so to speak. Such links may be terrestrial radio links, e.g., for transmitting television signals from the studio to the transmitter, or links including a satellite, or cable links, e.g., in cable television networks.
In any case, these links end at a transmitter which supplies the domestic receivers via separate video and sound channels.
To extend this system beyond the transmitter up to the domestic receivers, it was proposed in the application No. P 25 29 728.3 for a patent of addition to provide the present domestic receivers, during the transition period until the introduction of new domestic receivers capable of processing the composite video-sound signal, with added facilities which convert the received video-sound signal to the standard form, extract the sound signals, and feed the video and sound signals so obtained to the domestic receiver separately. This is an expensive solution, however.
On the other hand, it has been proposed ("Funkschau" 1974, No. 11, p. 398 bottom right) to transmit during the transition period, in addition to the composite video-sound signal, the sound signals from the transmitter to the domestic receivers on a separate sound channel as in the past.
It is a prerequisite therefore that the domestic receivers presently in use be capable of receiving at least the video signals of the composite video-sound signal correctly. With the signals transmitted in the known system, this is impossible.